The present invention relates generally to the field of automated packaging apparatus, and particularly to apparatus for automatically packaging pharmaceutical products such as capsules and tablets. Typically, such products are packaged in multiple cavity packaging units, such as "blister" packages. A blister package usually comprises a clear plastic film in which dimples or cavities are formed, the dimples or cavities shaped to accommodate a product of a particular size and shape. For example, a common blister pack comprises eight cavities filled with tablets. The product, e.g., a capsule or a tablet, is individually placed into a separate cavity within the plastic film. When automated packaging equipment is utilized, the placement of product in the package is typically accomplished by means of a vacuum transfer machine. Next, the package is sealed by covering the apertures of the cavities with suitable backing material such as, for example, paper-backed foil. The backing is then fixed to the plastic film by forming a heat seal around the periphery of a pre-defined area encompassing a number of cavities. Finally, the periphery of each blister package is cut to a smooth edge.
A significant problem with the aforementioned methods and apparatus is the inefficiency caused by partially-filled blister packages. A partially-filled blister package occurs when, due to imperfections in the system for automatically filling the cavities with product, one or more of the cavities is not filled. When partial filling occurs, absent corrective measures being taken, the partially-filled package must either be discarded or manually separated from the fully-filled packages. If the latter course is taken, i.e., if the partially-filled packages are manually separated out, the defective packages must be unsealed and the capsules or tablets recovered therefrom. If the partially-filled package is discarded, any capsules or tablets contained therein are lost. In any event, partial filling of the blister package causes product waste and the expenditure of additional labor, resulting in higher cost to the consumer and less profit for the manufacturer. Therefore, it would be desirable to provide methods and apparatus that automatically detect empty cavities in blister packages, and automatically recover product from the packages before they are sealed.
The use of a vacuum system in conjunction with material handling and inspection apparatus is generally known. For example, U.S. Pat. No. 3,884,011--Bardo et al. discloses the use of a vacuum-based system for handling and emptying envelopes. Included in the system is a means for detecting whether an envelope has been emptied and, if not, means for rejecting and separating the reject from the rest.
As another example, U.S. Pat. No. 4,559,754--Bacon, discloses apparatus for inspecting loaves of wrapped bread. In the apparatus disclosed, a photoelectric unit 32 is used along with vacuum means 28,30, a conveyor belt 16, and a pusher plate 38 to detect the absence of a properly tied end of the bread wrapping 14. The wrapping end under inspection is pulled away from the loaf 12, by the vacuum 30, as it is carried by the conveyor belt 16 past the photoelectric unit 32. The straightened-out wrapping interrupts the beam of the photoelectric unit. By measuring the duration of time that the beam is broken, the apparatus detects improperly tied ends. The pusher plate 38 is actuated when an improperly tied end is detected, and pushes the loaf into one of two chutes 42,44, from where it can be recovered and properly tied.
Therefore, although certain defect detecting apparatus are known within various production arts, an unmet need remains for providing methods and apparatus for detecting unfilled cavities in blister packages which enables such partial filling to be remedied without product waste or the expenditure of additional manual labor.